The present invention relates generally to intravascular guide wires. In particular, the present invention relates to guide wires having a lubricous hydrophilic tip and a less lubricous intermediate portion proximal the distal tip.
Guide wires are used in various procedures within various conduits in the body. In particular, they are used in Percutaneous Transluminal Coronary Angioplasty (PCTA) and other coronary procedures. This can involve inserting a guide wire through an incision in the femoral artery near the groin, advancing the guide wire over the aortic arch, into a coronary artery, and across a lesion to be treated. Guide wires can be inserted directly into the vasculature or within a guide catheter. The distal end of the guide wire ultimately lies directly within the vasculature.
Guide wires serve to guide devices into position for both therapeutic and diagnostic purposes. For this to happen, the guide wire itself must be properly positioned. This is difficult, as it involves moving a wire tip through a narrow opening within a narrow vessel, from 180 centimeters away. This task can be especially difficult as the guide wire must be extremely flexible at the distal end to enable the guide wire tip to enter vessel branches at various angles. The extreme flexibility can come at the expense of axial or rotational strength. Improved responsiveness to remotely applied forces, both rotational and axial, has been provided by reducing friction along the guide wire length. In particular, providing a highly lubricous guide wire distal region of about 12 inches has proven advantageous in maneuvering guide wires through the arteries to reach the site of blockage. Having this same lubricous coating on the tip of the wire has been advantageous in making the wire perform better in finding small openings in the blockages and crossing them.
Once the guide wire tip is in position, devices including catheters are advanced into position over the guide wire and withdrawn over the guide wire. Such catheter movement acts upon, and tends to move, the guide wire contained within. This can tend to dislodge the guide wire tip. Minor patient movement including breathing also acts to move the guide wire as does handling of the guide wire proximal portion extending from the patient. Dislodging the guide wire tip may require repositioning the guide wire, with the attendant time and effort. Once in position, therefore, stability and resistance to applied forces is preferred over the initially desirable ease of movement and responsiveness to applied forces.
What is desirable and has not been provided is a guide wire easily maneuvered into position across a tight lesion, yet providing stability and resistance to movement once the guide wire is in position.
The present invention provides a guide wire having a highly lubricous distal portion, followed proximally by a less lubricous intermediate portion, followed proximally by a proximal portion. The guide wire includes a core member within, preferably formed of metal and having a proximal constant cross section portion, followed distally by a tapered portion, followed distally by a reduced cross section portion. The tapered portion can have multiple tapers. The distal end of the reduced cross section portion is preferably flattened into a ribbon, providing greater flexure in one plane. A preferred core has a circular cross section in the proximal and tapered portions. One guide wire embodiment has a intermediate and distal portion length totalling about 12 to 14 inches. A preferred length for the distal portion is about 1 to 3 centimeters.
A preferred guide wire achieves a lubricous distal portion by having a hydrophilic surface in the distal portion. A less lubricous intermediate portion is achieved by having a hydrophobic surface in the intermediate portion. The hydrophilic surface has a very low coefficient of friction when placed against an artery wall in a blood filled artery. The hydrophobic surface has a higher coefficient of friction against the artery wall.
The present invention distal portion can be formed of a polymer not necessarily hydrophilic, but having a hydrophilic coating thereover. The intermediate portion can be formed of a hydrophobic polymer sleeve over the core wire or a polymer sleeve over the core wire having a hydrophobic coating. In another embodiment, the intermediate portion can include a coil around the core wire, the coil preferably having a hydrophobic coating. The coil wire abuts the distal portion in one embodiment, and is embedded beneath the distal polymer in another embodiment. In yet another embodiment, the distal portion includes a distal tip having a proximally tapered proximal portion, and the coil wire distal end contacts the distal tip in the tapered portion, thereby centering the coil.
The present invention provides the ability to cross tight lesions by having a highly lubricous, low friction, distal portion, which is relatively easy to slide through a narrowed vessel region. The extremely lubricous portion is limited to a shorter length relative to previous devices. A preferred length is about 1 inch. The lubricity is limited to the portion where the extreme lubricity is most needed, the distal portion. Lower friction is required in the extreme distal portion because the core member there is narrower and therefore weaker, not having the strength of the more proximal portion to handle being axially pushed from the proximal end against obstructions. Low friction is also required in this portion because this is the portion that is required to initially cross an extremely tight lesion, something not required of the more proximal portion. The low friction facilitates the wire tip first piloting into the small remaining opening in the lesion and then crossing the lesion without buckling the wire.
To counteract the highly lubricous, low friction distal portion, the present invention deliberately provides a less lubricous, higher friction intermediate portion, proximal of the distal portion. The intermediate portion can lie against an artery wall, or guide catheter wall, xe2x80x9canchoringxe2x80x9d the guide wire. The present invention, by having an anchoring portion proximal of the distal portion, provides resistance to forces such as catheter movement over the guide wire, which could act to dislodge the guide wire tip from its desired position.
While the anchoring portion friction will not prevent all movement of the guide wire, it provides sufficient static friction to resist unintentional movement due to either catheter movement or patient movement. In this way, a series of minor forces acting on the guide wire proximal portion, if below the threshold of static friction presented by the anchoring portion, will not be translated into a series of minor movements of the guide wire distal tip.